Diaphragm-holder for telephones



(No Model.)

S. W. HOLMAN.

DIAPHRAGM HOLDER FOR TELBPHONBS. No. 496,224. Patented Apr. 25, 1893.

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STATES PATENT OF ICE.

SILAS WV..HOLMAN, OF, BOSTON, MASSACHUSETTS.

DIAPHRAGM-HOLDER FOR TELEPHCNES.

SPECIFICATION forming part of Letters Patent No. 496,224, dated April 25, 1893.

Application filed November 5, 1892. Serial No. 451,021. (No model.)

To all whom it may concern..-

Be it known that I, SILAs W. HOLMAN, a citizen of the United States, residing at Boston, in the county of Suffolk and Commonwealth of Massachusetts, have invented a new and useful Improvement in Diaphragm- Holders for Magneto-Telephones, of which the following description is a specification.

It is well known that magneto-telephones, socalled, in which both the transmitter and receiver are magneto instruments, can emit sounds from the receiver which are'very clear and distinct, but which, as compared with sounds produced where a microphone transmitter is used, are deficient in loudness or volume, and it has been-considered very desirable to increase the loudness of the magneto telephone while retaininga satisfactory quality of articulation. I have devised a new method of holding the diaphragm of a magneto telephone instrument by which this desirable result is secured.

Heretofore, metallic or other plate diaphragms for magneto telephones have been held by firmly pinching an annular section of their outer edges between two fiat surfaces, usually rings of the same diameter. I believe that such diaphragm holderscause an unnecessarily large absorption of the energy of vi bration of the diaphragm, and thus reduce the amount of such energy of vibration available for conversion into electrical energy'in the transmitter, and for emission to the ear in the receiver, and I find that the substitution therefor of my improved diaphragm holder increases the 'efficiency of the telephone in a marked degree.

My invention consists first in the use of bearings with which the surface of the plate diaphragm will make only tangential contact and second in arranging these bearings on opposite sides of the diaphragm at different distances from the center, with the one of smaller diameter upon the same side of the diaphragm as the magnet, so that the spring of the plate will be in opposition to the pull of the magnet.

In the drawings accompanying this specification, Figure 1,is a central longitudinal section of a magneto hand telephone containing my improved construction of diaphragm holder. Fig. 2, is a diametrical section of a simple form of magneto-transmitter containing my improved holder. Fig. 3, is an enlarged view of the usual diaphragm and manner of holding it. illustration of the eifect of the magnet upon such a diaphragm. 13g. 5, illustrates the most satisfactory form of my improved diaphragm holder without the magnet, the bearings being substantially knife edges. Fig. 6,

is the same, showing the effect of the magnet Fig. 4, is an exaggerated upon the diaphragm. Figs. 7, 8 and 9 illustrate three different forms of bearing edges e for the diaphragm which may be used in my improved holder.

In Figs. 4. to 9 the curve of the diaphragm is greatly exaggerated, in order to better show.

to the eye the effect of the improved holder and the magnet upon the diaphragm;but in practice the deflect-ion of the diaphragm is Very small.

Referring to the drawings by letter; in Fig. I

1,A, is the diaphragm end of a magneto hand telephone which I find it advantageous to make of metal; B is the cap or mouth piece;

D the diaphragm of iron or other suitable flexible plate; upon the surface of the portion.

A, against which the diaphragm D, bears, I form a continuous ridge 0, and upon the inner surface of the cap B, I form another continuous ridge E. The diaphragm being put in place and the cap B screwed upon the part A, the ridge E will bear upon the diaphragm near its outer edge and press it down upon the ridge 0, and by the leverage thus obtained tend to strain the middle portion of the diaphragm over the magnet poles P, in a direction opposite to the stress exerted by the magv 9 net. The magnet M is supported by screwss through the metal portion A.

In the transmitter, Fig. 2, A, may be a metal ring or frame, the cap or mouth-piece B, be-.

ing held in proper relation thereto by screws ICQ Various other forms of bearings may be used, some of which are illustrated in Figs. 7 to 9,but substantially a knife edge seems best; also the outline of the bearing maybe varied; but by as much as it departs from a true circle by so much are the benefits of my improvements lost, and the least benefit over the old form is obtained when such bearings inclose areas of the same diameter, so that they will be directly opposed to one another upon the two sides of the diaphragm.

In Fig. 9, the edge of the disk diaphragm bears upon the inclined surface of the upper support which serves the purpose of an an gular or knife edge bearing upon the diaphragm and will come within the expression tangential contact as I intend it to be understood.

My improvements are to be distinguished from the construction heretofore used in which membrane and other diaphragms have been held, by being clamped at their outer edges between two rings, and then a straining ring of smaller diameter than the clamping rings pressed against the surface of the diaphragm: for diaphragms held in this manner do not give materially better results, so far as the energy of vibration is concerned, than those held without the straining-ring, excepting in the case of membrane diaphragms; but these cannot be employed beneficially with my improved construction, for the reason that it in no wise clamps or pinches the diaphragm between the bearings; but they hold it by merely resting against its opposite surfaces, thus leaving the plate diaphragm free to be bent over the sharp edges of the bearings, as it is set into vibration when the telephone is in use.

I claim 1. In a magneto telephone instrument the combination of a plate diaphragm, a magnet which tends to deflect the middle of the diaphragm in one direction from its normal state, and opposed supports with which the diaphragm makes tangential contact only, and which tend to deflect the diaphragm in the other direction from its normal state, substantially as described.

2. In a magneto telephone instrument, a plate diaphragm, a pair of opposed rings of different diameters which hold the diaphragm under tension in one direction byits tangential contact with each, and a magnet which holds the diaphragm under tension in the opposite direction substantially as described.

3. In a magneto telephone instrument, a plate diaphragm,apair of knife edge annular supports of different diameters which respectively bear upon opposite sides of the dia phragm and a magnet upon the side with the smaller annulus for the purposesubstantially as described.

SILAS W. I-IOLMAN. Witnesses:

WILLIAM W. J AcoUEs, A. J. BUnnoW. 

